For instance within the brewing and food production industries are used mainly cans at least one of the ends of which is without a lid. Such lids are subsequently applied to the can e.g. by being clamped to the filled can. Like the rest of the cans such can lids more often than not are not manufactured at the place of filling and subsequent closure of the cans. In order to allow such can lids to be handled in a convenient manner, it is important that they are appropriately packaged. One important aspect is to ensure that the infeed of lids into the lid application and attachment apparatuses is simple, that the lids are prevented from turning, ensuring that they face the same direction during the filling and in that the lids are kept clean during transportation to avoid the risk that during filling the can contents will be polluted via the lids. The latter requirement could possibly be less severe, were the lids cleaned prior to application. However, such procedure is not common practise and the users require that the can lids, when delivered, are sufficiently clean to allow direct application.
For the above reasons can lids are since long packaged in elongate bags the internal circumference of which only slightly exceeds that of the can lids. For some time these bags have been made from paper, a material which has proved to operate well and which also is advantageous from an environmental point of view. One end of the bags is closed, normally by folding the bag end and gluing said folded end to the face of the bag. A varying number of can lids (normally 2-600) are then introduced into the bag through the open end thereof, whereupon also this bag end is closed and the now completely filled package is placed on loading pallets to be transported to breweries and other lid users. The closure of the open end through which the lids are inserted into the bag has been effected in many different ways over the years. An early and still very common method is to simply fold over the upper not filled length of the bag and to maintain the closed condition by depositing the bag on the pallet with the folded bag length facing downwards. In this manner a bag end self-locking effect is achieved, which functions satisfactorily when the packages are handled manually.
Gradually, however, an increasing number of the operational steps of the can lid handling process has been automated. Methods have been developed to automate e.g. the packaging of the can lids into bags and to position such bags on loading pallets. A device for this purpose is described for instance in the Applicant's Swedish Patent Application 9401920-5. As already mentioned, also the application of the lids onto the cans is effected by mechanical means. The automation has increased the requirement on package strength and consequently in principle the method used exclusively today is one which has existed and been used for several years, viz. gluing or taping of the folded-over end flap to the bag.
This method of packaging the can lids and above all the method used to close the packages does, however, involve several drawbacks. For instance the folded-over portion of the bags gives the bags an uneven thickness which in turns causes problems when the bags are to be palletised. In addition, this closing method makes it difficult to develop methods for automated opening of the bags and emptying the lids into the lid application apparatus. However, attempts have been made to automate also this step of the handling process. Devices designed for this purpose are described for instance in the U.S. Pat. Nos. 4,997,329 and 4,245,946. In the first mentioned specification is described a manner for cutting open the bag along its entire length, whereupon the can lids may be removed from the bag. The latter specification describes a devise allowing the closure to be opened by pulling apart the glue bond between the folded-over flap and the bag, whereupon the lids may be withdrawn from the bag through the same opening as that through which they were inserted, A common feature found in both these prior-art devices is, however, that they are expensive and complicated to manufacture (particularly the latter one) and above all, that the reliability of the devices is poor, which cannot be accepted by the users as this causes recurrent disruptions of the processes. Consequently, only a small number of the users employ apparatuses of this or similar type whereas the absolute majority of the users still open the bags and charge the can lids into the lid-application apparatuses manually.